Screening Of Lactobacillus Fermentum For Probiotic Potential And Study On Fermentation Characteristic In Soy Milk

Ninty strains of Lactobacillus fermentum were isolated from traditional dairy products of Chinese minority nationalities(53 strains from Tibet, 1 from Inner Mongolia, 7 from Yun Nan and 29 from Mongolia), and the resistance of the strains to acid, simulated gastrointestinal juice, bile salts , were evaluated. The proper probiotic 11 strains be selected to research the properties of antimicrobial and coaggregation. Furthermore studied on soy milk fermentation characteristic and senses qualification.The results showed that 35 strains of Lactobacillus fermentum grew well at acid condition (pH 3.0).Among the 35 strains, 11 strains showed high tolerance to the simulated gastric juice (pH2.5, 3h of incubation). The incubation of the 11 strains in the simulated gastric juice (pH2.0, 3h of incubation) showed that only F6 (isolated from traditional dairy products in Inner Mongolia) could survive with a survival rate of 53.68%(after 3 hours). The highest concentration of bile salt that F6 can resist was up to 1.8%,The later time is 0.66h in 0.3% concentration of bile. Among 11 Lactobacillus strains, F6 showed well tolerance to bile salt.Further antimicrobial and coaggregation activity of the strains were evaluated. All of the selected strains showed various antimicrobial activity against food-borne pathogens, and F6 possessed the highest ability of inhibit pathogens. All strains showed high autoaggregation percentage after being incubated at room temperature for 20h.Then the selected strains were tested as starter culture for the fermentation of soybean milk. The live bacterial cells of soy yoghurt by F6 could achieve as much as 1.0×108 CFU/mL after fermented 15h. During storeage process, there was no whey separated, the surface was exquisite, the stretchability was favourable, the viable count didn't decrease obviously and the viscosity was more significant than others.(P<0.05).Our results indicated that L.fermentumF6 showed good probiotic potential for application in functional foods and health-related products.